400 Amp Service

[John Valdes]

I looked at a job today. The homeowner wants an upgrade from 200 Amp to 400 amp. There are 2 seperate structures connected by a breezeway. The existing buried service laterral is positioned where upgrading would be very difficult. I reccommended that he move the service to the garage where it would be a straight run from the POCO xfmr. One 50' trench. Then make the house main service panel a sub panel. I am pretty sure this would not be a violation? But the garage has no plumbing and I would have no water pipe to bond to. Must I have a water line or would 2 grounding electrodes be allowed. The home is piped in copper. The breezeway is only for appearance and is not over either structure door. However, the breezeway does share an overhead crawl space with both structures
Does anyone see any problem with my reccommendations?

ps......The homeowner would prefer a seperate meter for the garage and leave the house as is. But according to the AHJ, both structures are considered as one structure, therefore only one service drop is allowed?

 

[infinity]

If the breezeway connects the garage and the house together they are one structure. What does the POCO say about moving the service? Your idea seems to be code compliant, just keep in mind that the existing panel that will become a subpanel will now require a separation of grounded and EG conductors.

 

[normbac]

Did similiar job, house was considered attached to garage- studio because it has an attic to and from each structure The 200 was used as a panelboard and the meter was left on to charge renters. we isolated the ground bars and drove a rod at the 400 panel. We did have to run a bond through attic to water and gas though. This seemed to be the cleanest application

 

[mdshunk]

I see that as clearly one structure. Exactly where to place the service is a matter of personal preference combined with PoCo rules. Most or all of the PoCo's that I work under want it within 15 feet of one of the front corners of the house. In your case, that would be on the end of the garage, where you said it would be easy to put it. I see this as a no-brainer. Build your service on the end of the garage, and subfeed the existing panel through that attic space.

 

[suemarkp]

The water pipes will require a #2 or 1/0 copper bond wire depending on the exact service conductor size used. You can either run it separately from the house feeder, or use a 1/0 copper EGC in the feeder to the house and then continue the water bond from the grounding bus in the house panel.

But if the water pipe is metal outside for 10' or more, then you have to use it as an electrode and not just bond it. Same size wire requirements, but no splices allowed. So you'd have to run a 1/0 unspliced from the service all the way to the water pipe and within 5' of where it enters the house. This won't be a very effective service ground (run is too long), but that's the rules.

Regardless of the water pipe, you need an additional electrode. If you don't have one, then two ground rods is what you do.

 

[John Valdes]

Okay. But my concern is the electrode and water pipe conductor. There are no water lines in the garage. The main panel that will become a sub panel, is bonded to the water line at the house.

My question would be, do I need to run a bare conductor all the way from the garage (new 400 amp main) to the house, to access the water line? Or can I just connect to the two ground rods at the new service and leave the existing main (new sub panel) bonded to the water line. I plan to run a four wire feeder back to the house, and seperate the grd and neutral. Since the garage has no water but the house does, is what has me asking.

normbac.....You had to run a bonding wire through the attic crawl space? Did you include it in the conduit pull or did you seperate it and how?

Sorry guys if I am not making much sense......John

 

[Dennis Alwon]

Yes, you would have to bond the water lines at the house with either a #2 copper or 1/0 copper depending if you have 2 200 amp panels or an all in one panel meterbase 400 amp. You still need the 2 rods and the panel at the house would need 4 wires.

As others have said this is one structure.